Account Polarization Effects Research Articles

Solving a Dyson integro-differential equation for elastic electron scattering on the sodium cluster Na8

Electron scattering on metallic clusters, at low and very low energies, is described within the many-body framework of Dyson equation, taking then into account polarization and exchange effects. A direct solution of the resulting integro-differential equation is presented for the first time. Phase-shifts and cross-sections are calculated for closed shell sodium cluster Na 8 and compared with previous calculations using different levels of approximations.

Phase induced intensity noise in concatenated fiber-optic delay lines

A fiber-optic differential-delay-line structure converts the phase noise of its short coherence source to intensity noise at its output. If this structure is followed by a similar system, intensity noise is generated as well as filtered by each of the two systems. The power spectrum of the noise at the output of concatenated systems built of Mach-Zehnder and the recirculating delay lines is theoretically studied. The spectral structure of phase-induced intensity noise at the output of these concatenated systems is analyzed, taking into account polarization effects and emphasizing the physical interpretations of the results. An experimental verification is presented for the case of two recirculating delay lines in series.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

A multichannel theory for the free-free transitions of an electron in the field of an atomic system

The theory of the free-free transitions of an electron in the field of a general atomic system is developed using Racah algebra. General expressions, taking into account polarization and angular distribution effects, are obtained for the cross sections. The relevant, matrix elements for atomic systems with ground state configurations npq(n=2,3) are discussed within the framework of the close-coupling approximation.

On a simplified effective neutron-proton interaction including core-polarization effects for odd-odd deformed nuclei

It is well known that the description of odd-odd deformed nuclei is not satisfactory if the usual one-parameter δ-force is used as the residual neutron-proton interaction. In this letter we show that, starting with a simple δ force, an improvement can be obtained which takes into account polarization effects of the core, as well as possible tensor and spin-orbit force effects, and which introduces only one additional parameter. This improvement is even better than that obtained with a finite range central-plus-tensor force, which introduces four additional parameters.

On a simplified effective neutron-proton interaction including core-polarization effects for odd-odd deformed nuclei

It is well known that the description of odd-odd deformed nuclei is not satisfactory if the usual one-parameter δ-force is used as the residual neutron-proton interaction. In this letter we show that, starting with a simple δ force, an improvement can be obtained which takes into account polarization effects of the core, as well as possible tensor and spin-orbit force effects, and which introduces only one additional parameter. This improvement is even better than that obtained with a finite range central-plus-tensor force, which introduces four additional parameters.

Plasmon Damping in Metals

A report is given of a theoretical and experimental investigation into the degree of plasmon damping in metals as a function of momentum transfer. A previous theoretical result by DuBois is corrected and extended by taking into account polarization effects. Measurements are reported of the change in half-width $\ensuremath{\Delta}{E}_{\frac{1}{2}}$ of the dispersed \ensuremath{\approx}15-eV aluminum plasmon energy-loss peak, excited by 20-keV electrons, as a function of electron scattering angle $\ensuremath{\theta}$. The results can be expressed in the form $\ensuremath{\Delta}{E}_{\frac{1}{2}}=A+B{\ensuremath{\theta}}^{2}+C{\ensuremath{\theta}}^{4}$, and there is good agreement between the values of $B$ and $C$ obtained from the revised theory and those found experimentally.

Polarization in Nuclear Reactions

In order to take into account polarization effects in the scattering of low energy neutrons by medium and heawy nuclei, the square well optical model was modified by adding to the potential a spin-orbit term. (W.D.M.)